This invention relates to printed circuit board connectors and, more particularly, to an improved coaxial connector for use with a printed circuit board and adaptable for single or double sided use.
In present day computers, which use very large scale integrated (VLSI) circuits, signal propagation times are very critical. In particular, it is essential to provide close and accurate timing for pulse coincidence at the inputs to logic gates. At a minimum, a pulse overlap of two thirds of the signal width is required in order to get useful pulse coincidence, since smaller overlaps lead to low confidence levels and errors. In many present day computers, the pulse width is on the order of two nanoseconds or less, and the propagation delay in the interconnecting media, whether circuit boards or cables, has a significant impact on the timing after repair or replacement of a board. As a further complication, the accuracy of pulse coincidence is subject to degradation when a semiconductor device on a board is replaced, since switching times and propagation delays of complex semiconductors may vary from device to device.
In older slower systems, pulse coincidence was achieved by varying the conductor length in the interconnecting media. In other words, the interconnecting media was treated as a variable delay line. However, when the pulse width is very narrow, the tolerance range is also narrow and cannot be satisfactorily handled by a fixed length delay line. Since the lengths of the conductors on a printed circuit board are not adjustable, then if a component is replaced by one with a different propagation delay, timing adjustments must be made. These adjustments frequently have to be made in the field, not at the point of manufacture, and require an external adaptation of the delay line. Such adaptation is typically accomplished by trimming the length of either twisted pairs or a coaxial cable to a length which provides the necessary time delay to assure pulse coincidence.
As previously described, the ability to be able to adjust timing is fast becoming a necessity for many of the logic connections on the printed circuit boards of computers. Accordingly, what is required is a coaxial connector (frequently referred to as a launcher) which can be installed at various locations on the printed circuit board. This installation must be accomplished in the field. Present coaxial connectors (or launchers) are typically bulky devices, consisting of a machined casting or part, which is of substantial bulk, occupies substantial space, and represents substantial cost. It is therefore a primary object of this invention to provide a signal launcher for a printed circuit board which is of low cost, low bulk and installable at high density.
It is another object of this invention to provide such a signal launcher which may be installed in the field with automatic compensation for board thickness variation.
It is a further object of this invention to provide such a signal launcher which requires no soldering upon installation.
It is still another object of this invention to provide such a signal launcher which can be installed on either side of the printed circuit board.
It is yet another object of this invention to provide a signal launcher which can be installed on both sides of a printed circuit board to provide a signal feed-through.